1. Field of the Invention
The invention relates to atomizing apparatus wherein a liquid is dispersed into a fine mist by an atomizing medium, the invention being particularly useful for increasing combustion efficiency of a liquid fuel or the like. The present invention more expressly relates to an aerodynamic atomizer structure wherein a first flow of atomizing medium moving at sonic velocities imparts maximum aerodynamic shear to a liquid in a first atomization zone and wherein a second flow of atomizing medium downstream of the first atomization zone is directed against the mixture of atomizing medium and liquid to disperse and redirect the emulsified liquid.
2. Description of the Prior Art
Practical considerations made even more compelling by the need to conserve dwindling fossil fuel energy resources require that presently used fuels be burned as efficiently as possible. Since the fuels which are primarily used for burning in home and industrial furnaces are becoming increasingly scarce, it is also necessary that fuel sources be developed and utilized which have not previously been capable of being efficiently burned with available burners. Materials such as asphalt and the like which have previously been considered as being suitable only for use as road fill are known to contain substantial quantities of energy. However, it has not been previously possible to efficiently burn such materials without producing substantial pollution and without harm to the burner due to the production of unburned products of combustion which foul burner mechanisms. While certain presently available burners are being employed to burn these "lower grade" materials, the situation is not satisfactory due to the facts of increased pollution, hardware deterioration, and other operational problems.
While the present invention can be used for atomization of any fluid, it is particularly to be noted that the present structure is useful for atomization of a liquid fuel immediately prior to combustion in order to maximize combustion efficiency. In a basic sense, combustion is seen to be the rapid chemical combination of oxygen with the combustible elements of a fuel. The objective sought for in combustion processes is the release of all heat available in the fuel which is being burned. In order to obtain this objective, it is necessary to minimize losses from combustion imperfections and superfluous oxidizing medium. In practice, it is attempted to maximize combustion efficiency by the provision of sufficiently high temperatures for efficient ignition, the subjection of the fuel to efficient mixing with the oxidizing medium, and the provision of sufficient time to allow complete combustion between the fuel and the oxidizing medium. The most difficult of these factors to retain is the mixing of the fuel with the oxidizing medium in a manner sufficient to maximize combustion efficiency. A particular method which has been used to provide a more intimate contact between fuel and oxidizing medium is the atomization of liquid fuel into the smallest possible droplet form, thereby to decrease the time per unit volume for conversion from a liquid to a gaseous state. The fuel in the gaseous state is thus capable of more intimate mixing with the oxidizing medium.
High burning rates have previously been established with the injection of atomized fuel into regions of high turbulence and high shear. Atomization structures, such as that disclosed in U.S. Pat. No. 3,912,164, act to create regions of high turbulence and high shear by producing swirling air streams which produce regions of high turbulence and high shear at locations where the streams meet. According to this particular patent, relatively efficient atomization is caused by exposing a thin continuous sheet of fuel to high velocity air on both sides of the sheet of fuel.
Fuel atomization structures are also seen to be disclosed in U.S. Pat. No. 3,831,843. As is recognized in this patent, only a very small percentage of the total kinetic energy of the atomizing medium is typically imparted to the fuel. Since combustion intensity and efficiency is primarily determined by the average surface area of fuel particles in contact with oxidizing medium, the time required for the evaporation of liquid fuel droplets is critical when atomized fuel is being burned. Combustion efficiency is seen to increase with reduced fuel droplet size. However, no known prior art atomizing structure has been capable of producing efficient atomization of materials such as coal/oil slurries, asphalt and the like. An atomizing structure capable of producing fine particles of such materials would dramatically increase the availability of fuels for certain combustion applications. Further, such atomizing structure would more efficiently burn those fuels which are now used in these combustion applications. The present invention provides atomizing structure which is capable of efficiently burning previously unusable materials which have been used in applications such as roadbed fill since the means for utilizing the materials as fuel did not exist. The invention particularly subjects the fuel to contact with two separate flows of high velocity atomizing medium in order to efficiently emulsify and disperse the fuel prior to combustion.